Cannot parent my mesh to armature with automatic weights
The problem is mostly due to the fact that both the rig and the mesh aren't perfectly symmetrical, you have to make sure both your mesh and your rig are properly lined up.

I recommend makign sure the central row of vertices of your model are straight, by scaling along X to 0, then line up the bones in the central column of your armature, delete the limbs of either side, and make sure you can properly skin one half.

Then follow this answer on how to properly mirror a rig

as a side note, your thumb bones aren't attached to your hand bones, and you have some aberrant geometry on the hat and on the neck watch out.